4. Clinical Characteristics of COVID-19

4.1. Clinical Manifestations
According to the “Diagnosis & Treatment Scheme for Novel Coronavirus Pneumonia (Trial) 6th Edition” enacted by the National Health Commission of the People’s Republic of China on 19 February 2020, the incubation time after exposure is about 1–14 days [20]. Fever, fatigue, and a dry cough are the main manifestations. Nasal obstruction, runny nose, and other upper respiratory symptoms are rare. About half of the patients developed dyspnea one week later, and severe cases developed rapidly into acute respiratory distress syndrome, septic shock, hard-to-correct metabolic acidosis, and coagulation dysfunction. Severe and critical patients may present moderate to low fever, or even no obvious fever. Some patients have mild onset symptoms, no fever, and mostly recovered after one week. Most patients have a favorable prognosis, although some patients are left in a critical condition, or do not survive. The aged patients and the patients with basic diseases have worse prognosis. Children cases are relatively mild.

4.2. Laboratory Examination
In the early stages of the disease, the total number of leukocytes in peripheral blood is normal or decreased, the lymphocyte count is decreased, and some patients present elevated levels of liver enzyme, muscle enzyme, and myoglobin; some severe cases present elevated troponin level. Most patients show elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), and normal procalcitonin. In severe cases, the patients present with increased D-dimer and progressively decreased peripheral blood lymphocyte [20]. Compared with non-ICU patients, the plasma levels of IL2, IL7, IL10, GSCF, IP10, MCP1, MIP1a, and TNF-α were higher in ICU patients [21].

4.3. Chest Imaging
All patients suffered from pneumonia, and chest CT scans showed shadows in the lung [20]. In the early stages of the disease, patients present with multiple small patch shadows and interstitial changes, especially in the extrapulmonary zone. It further progresses to multiple ground glass shadows and infiltrative shadows in both lungs. In severe cases, lung consolidation may occur, but pleural effusion is rare [20].
To provide more information about the disease for the treatment in clinics, we collected detailed information about the fatal cases released by official channels. A total of 41 fatal cases were used to reveal the symptoms of the deaths, showing the symptom composition of fever (80.5%), cough (56.1%), short of breath (31.7%), chest tightness/pain (24.4%), fatigue (22.0%), dyspnea (12.2%), dizziness/headache (4.9%), general pain (7.3%) and chills (4.9%) (Figure 2). A total of 26 cases with fatalities were used to disclose the dangerous comorbidities, showing that the major comorbidities are hypertension (53.8%), diabetes (42.3%), coronary heart disease (19.2%), cerebral infarction (15.4%), chronic bronchitis (19.2%) and Parkinson’s disease (7.7%) (Figure 2). Chen N et al. reported that, among 99 confirmed cases, the common symptoms are fever (83%), cough (82%), bilateral pneumonia (75%), short of breath (31%), muscle ache (11%), confusion (9%), headache (8%), sore throat (5%), rhinorrhoea (4%), chest pain (2%), diarrhoea (2%), and nausea and vomiting (1%) [4]. Huang C et al. reported that, among 41 confirmed cases, the symptom composition is as follows: pneumonia (100%), fever (98%), cough (76%), lymphopenia (63%), Dyspnea (55%), fatigue (44%), sputum production (28%), headache (8%), hemoptysis (5%), and diarrhea (3%); and the underlying diseases included diabetes (20%), hypertension (15%), and cardiovascular disease (15%) [21]. Though the symptom compositions reported for the confirmed cases are similar to that of the fatality cases we collected, the percentages of hypertension, diabetes, and coronary heart diseases are much higher among the fatality cases than among the confirmed cases. This may indicate that the comorbidities probably are important factors resulted in death of COVID-19 patients.